(1) Field of the Invention
This invention relates in general to coated substrates. In one aspect, this invention is directed to medical devices and other substrates having improved lubricious coatings. In a further aspect, this invention provides medical devices, such as catheters, guide wires and the like, which when dry exhibit little or no lubricity but when moistened, possess a lubricity which aids in moving the devices within the body with ease and little discomfort. In another aspect, this invention is directed to a process for the preparation of the coated medical devices which are useful in the diagnosis or treatment of various conditions in the human body.
(2) Description of the Related Art
Catheters which are used surgically for insertion through blood vessels, urethrea, or body conduits, and guide wires used with catheters for biopsy, balloon angioplasty and other medical procedures require a low-friction surface for preventing injury to, or inflammation of, mucous membranes and other body tissues.
One class of conventional catheters is made of low-friction materials such as TEFLON, polyethylene or other materials coated with a layer of TEFLON or silicone. There are two shortcomings of these catheters: First, they are not sufficiently slippery for the intended surgical purposes mentioned above. Second, they are difficult to handle and store because their surfaces are slippery at all times.
Another class of conventional catheters is rendered lubricious by coating with a layer of silicone fluid, glycerin, or olive oil. These materials are unsatisfactory because the low molecular weight additives tend to run off quickly. Thus, they lose the initial lubricity rather rapidly.
Another class of conventional surface treatment involves the deposition of poly(vinyl pyrrolidone) in the presence of a polyisocyanate. This type of coating while lubricious initially lacks abrasion resistance, and is therefore easily removed from the surface of the medical devices. An improved version of this technique was described by R. A. Winn in U.S. Pat. No. 4,373,009, where an active hydrogen containing vinyl pyrrolidone copolymer was used instead to result in a better bonding to the substrate. The "monomers containing active hydrogen" were needed according to Winn "to form a covalent bond between the coupling coating and the hydrophilic copolymer". These copolymers, however, were of unknown quality in terms of purity, toxicity, or not of sufficiently high molecular weight needed for this application. Both the availability and usefulness of these copolymers are highly questionable.
In U.S. Pat. No. 4,119,094, a substrate such as a tube or catheter is disclosed having a hydrophilic coating which exhibits a low coefficient of friction. The substrate is coated with a poly(vinyl pyrrolidone)-polyurethane interpolymer. A polyisocyanate and a polyurethane mixture is applied to a substrate and after drying, a poly(vinyl pyrrolidone) in solution is applied.
U.S. Pat. No. 4,589,873, issued on May 20, 1986 to A. Schwartz et al and discloses a method of applying a hydrophilic coating to a polymeric substrate. The coating consists of poly(vinyl pyrrolidone) which is applied to the substrate in a solvent followed by drying.
W. S. Creasy et al were granted U.S. Pat. No. 4,642,267 on Feb. 10, 1987 which discloses and claims a hydrophilic polymer blend. The blend is comprised of a thermoplastic polyurethane having no reactive isocyanate groups and a hydrophilic poly(N-vinyl lactam) such as poly(vinyl pyrrolidone The blend can contain additional polymeric components such as homopolymers or copolymers of monomers including vinyl chloride, acrylic acid, vinyl alcohol and the like.
A process for coating a polymer surface with a hydrophilic coating is also disclosed in U.S. Pat. No. 4,666,437. A solution of a compound containing at least two unreacted isocyanate groups per molecule is applied to the polymer surface and the solvent evaporated. Thereafter, a solution of poly(vinyl pyrrolidone) is applied to the treated surface and the coated cured.
According to European patent application 0166998, N. Takamura described lubricious coatings derived from either a cellulosic polymer, a maleic anhydride polymer, a polyacrylamide or a water-soluble nylon which were convalently bonded to a medical instrument substrate. The substrate contained reactive functional groups such as aldehydes, epoxy, isocyanate or amino groups. The reference indicates that the water soluble polymers are non-crosslinked and contain hydrophilic groups such as --OH, --CONH.sub.2, --COOH, --NH.sub.2, --COO--, --SO.sub.3 --, and --NR.sub.3, R being alkyl or hydrogen. However, a cellulosic polymer is undesirable because it must be protected against microbe attack. Coatings made from a maleic anhydride polymer must go through a tedious post treatment with water before developing lubricity, while water-soluble nylons may have questionable stability.
It has now unexpectedly and surprisingly been found that high molecular weight carboxylic acid-containing polymers or their partially neutralized salts, can be strongly bonded to a substrate, such as a catheter, using a polyisocyanate reagent and at the same time provides a hydrophilic lubricious coating. Thus, the need for either an interpenetrating network containing poly(vinyl pyrrolidone) and polyurethane or a copolymer containing both non-active hydrogen units and active-hydrogen units can be avoided. Furthermore, there is no need for any post hydrolysis treatment in the invention. Unlike a maleic anhydride polymer, the coating develops lubricity instantly upon exposure to an aqueous fluid. Poly(acrylic acids), such as the CARBOPOLS manufactured by B.F. Goodrich, are ideally suited for the intended medical applications, and also have sufficiently high molecular weights necessary for achieving both good hydrophilic lubricity and abrasion resistance.
Accordingly, one or more of the following objects will be achieved by the practice of this invention. It is an object of this invention to provide medical and other devices which when dry do not exhibit a slippery surface, but when contacted with a fluid such as water, become very lubricious. Another object of this invention is to provide medical and other devices which are easily handled without fear of slipping, but when moistened or contacted with body fluids instantly become very lubricious. A further object of this invention is to provide medical devices having a coating of a poly(carboxylic acid) and a polyisocyanate which when dried can be handled with ease, but when moistened, become very slippery. A still further object of this invention is to provide processes for the preparation of the coated medical and other substrates. Another object is to provide medical and other devices and instruments which have a coating of a material which becomes lubricious upon exposure to body fluids. These and other objects will readily become apparent to those skilled in the art in the light of the teachings herein set forth.